UNITED STATES FUEL ADMINISTRATION BUREAU OF CONSERVATION Engineering Bulletin No. 1 BOILER AND FURNACE TESTING Prepared by Ruftis T. Strohm Associate Editor, Power Maximum Production WASHINGTON I 1 3 fQ^P H rTnViT DUTMTfMn riKTiTr'Ti' GOVERNMENT PRINTING OFFICE 1918 MAXIMUM PRODUCTION,. MINIMUM WASTE, The United States Fuel Administration is making every effort, through the pro- ducers and transportation lines, to obtain an adequate supply of fuel for the industries of the country. Twenty-five to fifty million tons of coal a year can be saved by the improved oper- ation of steam-power plants without changing their present equipment and without abating their production the slightest. It is absolutely necessary that this saving be realized, if our overburdened railroads are to be relieved and our industries kept in full operation. The extent to which it will be realized depends upon the cooperation of the own- ers, engineers, and firemen of every power plant of the country. YOUR FIRING LINE IS AT THE FURNACE DOOR. DAVID MOFFAT MYERS, Advisory Engineer to United Stales Fuel Administration. BOILER AND FURNACE TESTING. By P.UPUS T. STROHM. NECESSITY FOR TESTING BOILERS. A boiler test is necessary in order to determine how well the boiler is doing the work expected of it; that is to say, we must find out whether we are wasting coal in making steam and how much this waste may be. Such a test may be made to discover the efficiency of the boiler, or the quantity of water it is evaporating, or the cost of evaporating 1 ,000 pounds of water. The United States Fuel Administration recommends that every boiler plant have some means of daily checking the efficiency of the boiler and furnace. The simplest and best way of finding out how efficiently the boiler is working is to make an evaporation test, as described in this bulletin. All the necessary records can be made automatically with suitable instruments, although in many small plants the coal must be weighed on ordinary scales. The efficiency of the furnace can be found by making analyses of the flue gases. (See Bulletin No. 2 of the United States Fuel Administration.) Too many engineers and firemen have the idea that they are not fitted to make boiler tests. This is altogether wrong. Any man who can weigh water and coal and read steam gages and thermometers is able to do the work required in making a boiler test for evaporation or efficiency. Such a test requires a knowledge of the following: 1 . The total weight of coal used. 2. x The total weight of water fed to and evaporated by the boiler. 3. The average temperature of the feed water. 4. The average steam pressure hi the boiler. If these four items are known, a series of simple calculations will show how much water is being evaporated per pound of coal, and the efficiency of the boiler and furnaqp. To make a test, the following apparatus and instruments are necessary : 1. Scales to weigh the coal. 2. ^Apparatus to weigh or measure the feed water. 3. Thermometers to take feed-water temperature. 4. Gages to indicate steam pressure. A boiler test to be of value should extend over a period of at least eight hours. The longer the test the more accurate the results. i For the sake of simplicity, only the essential elements of boiler and furnace testing are treated in this bulletin. For rules covering the refinements for an exhaustive test, the reader is referred to the boiler test code of the American Society of Mechanical Engineers. Copies of this code can be obtained from the secretary, 29 West Thirty-ninth Street, New York City. 3 BOILEE AND FURNACE TESTING. WEIGHING THE COAL. The weight of coal used during a test may easily be found by using an ordinary wheelbarrow and a platform scales, arranged as in figure i. At each side of the scales build an incline with its top level with the top of the platform, but take care not to have either one touch the platform. Set the empty wheelbarrow on the scales, run the movable weight or poise out until it exactly balances the weight of the barrow and lock it in position with the thumbscrew. Next, put weights on the scale pan A to correspond to a not weight of 250 or 300 pounds of coal. Fill the barrow with coal, run it on the scales, and add coal or take off coal until the scales balance. This is easily done by having a small pile of coal B beside the scales. If the weights on the scale pan represent, say, 300 pounds, the net weight of coal in the barrow is exactly 300 pounds. This coal ia 2 Actdfo balance net weight of coal 7 Set tobalairce tare of whee/barrovt wheeled in front of the boiler and dumped on the clean floor, and the barrow is returned for another load. Each time the barrow of coal is weighed on the scales and taken to the boiler being tested, a tally mark should be made on a board nailed to the wall beside the scales. Each tally mark represents 300 pounds of coal, since the amount^of coal in the barrow is adjusted at each weighing, so that the scales just balance. At the end of the test, therefore, the number of tally marks is multiplied by 300, and the product is the weight of coal used, provided it has all been fired; but if any coal remains in front of the boiler at the close of the test, it must be gathered up and weighed, and its weight must be sub- tracted from the total weight indicated by the tally marks to get the number of pounds of coal actually fired. You should, of course, start the test with no coal hi front of the boiler. Care must be taken not to forget to make a tally mark each time a barrow of coal is run off the scales. By setting the scales so as to show any net weight, such as 250 or 300 pounds, and making each bar- BOILER AND FURNACE TESTING. 5 row load exactly this weight, much time is saved, as it is unnecessary to change any of the weights or the position of the rider on the scale beam. If the coal used in the test is to be analyzed, take a sample of from 4 to 6 pounds from each barrow and throw it into a box near the scales Do this before the coal is weighed. These small amounts from the various barrow loads will then give a fair average sample of the coal used during the test. The condition of the furnace should be the same at the end of the test period as at the start. Therefore, at the moment the test is begun, observe the thickness of the fuel bed and the condition of the fire. If the fire was cleaned, say, an hour before the test began, see that it is cleaned an hour before the time when the test is scheduled to end. If the coal was fired, say, eight minutes before the test started, the last coal used during the test should be fired eight min- utes before the end of the test. The object of these precautions is to insure the same conditions at start and finish, as nearly as pos- sible; otherwise, the coal weighed will not be the same as the coal consumed. MEASURING THE FEED WATER. The quantity of water fed to the boiler during the test may be found by metering or by weighing. A reliable water meter is recom- mended for this work. There are a number of good makes, of differ- ent types, such as: 1. Venturi meter. 2. Weir or V-notch meters. 3. Diaphragm meters. 4. Displacement meters. 5. Water weighers. The best form of meter to use in any particular case depends on the local conditions in the plant; but every plant should be provided vriih a permanently installed meter of some type. The displacement form of meter should be used only with cold water, however. If there is no meter or water weigher in the plant, the feed water used during the test can be measured by the three-barrel arrange- ment illustrated in figure 2. Obtain three water-tight barrels, and set two of them close together on a platform directly over the third, leaving about 12 inches above barrel 3 in which to fit the valves V and the nipples in the bottoms of barrels 1 and 2. Near the top of each of the barrels 1 and 2 screw a 1-inch overflow pipe 0. Run a pipe P from the city main or other source of supply above barrels 1 and 2, and put a valve A on the pipe leading to each barrel. From barrel 3 run a suction pipe to the feed pump that is to pump water to the boiler to be tested. It is best to have a by-pass from 6 BOILER AND FURNACE TESTING. the usual water supply direct to the feed pump, or to another pump connected to the boiler, so that in case of any trouble with the test- ing barrels, the regular operation of the boiler may be resumed with- out shutting down. The next step is to fill barrels 1 and 2 with water until they over- flow at O. This water should be of practically the same average temperature as that which is to be used during the test. Barrel 3 should be high enough above the feed pump so that the pump will handle hot water. Put barrel 3 on a scales, before connecting it to the feed pump, and weigh it. Then let the water from barrel 1 run into barrel 3, and weigh again. The second weight minus the first weight is the net weight of water run in from barrel 1 and is the weight of water contained in barrel 1 when filled to the overflow. The weight of water in barrel 2 when it is filled to the overflow can be found in like manner. Mark these weights down. When the net weights are found and barrel 3 is removed from the scales and connected to the feed pump, the apparatus is ready to begin the test. Start with the level of the water about 1 foot below the top of the barrel 3, and drive a nail into the barrel to mark this level. When the test is finished, the level should be brought to the same point, so that the water that has passed through barrels 1 and 2 will accurately represent the weight of water fed to the boiler during the test. When the test is to begin, stop the feed pump and tie a string around the gage glass on the boiler to mark the height of the water level in the boiler. Then start the pump connected to barrel 3. Fill barrels 1 and 2 up to the overflow before the test is started. Then open the valve V on barrel 1 and let the water run into barrel 3 as fast as the feed pump draws water from barrel 3. When barrel 1 is emptied close its valve V and open its valve A so as to refill it. BOILER AND FURNACE TESTING. 7 While barrel 1 is filling empty barrel 2 into barrel 3 in the same way, and continue to fill and empty barrels 1 and 2 alternately. In this way barrel 3 will be kept supplied with water that has been measured in barrels 1 and 2, the net weights of which were found before the test began. Keep a separate tally of the number of times each of the barrels 1 and 2 is emptied into barrel 3. At the end of the test the number of tallies for each barrel multiplied by the weight of the water that barrel will hold will be the weight of water measured in that barrel. The sum of these weights for barrels 1 and 2 will be the weight of water used in the test. With a three-barrel arrangement like this, water can be weighed rapidly enough to supply 300 boiler horsepower. Before starting a test make sure that there is no chance for water to leak into or out of the boiler. See that the blow-off is tight, that there is no drip from gage cocks, and that the feed-line connections are tight, so that all the water fed to the boiler will represent accu- rately the amount evaporated during the test. If a meter is used instead of the three-barrel method, make abso- lutely sure that the meter is correct, as the accuracy of the test de- pends on the accuracy with which the water measurements are made. After a meter is installed, test it to see that it operates correctly under the plant conditions. The water level in the boiler should be the same at the end of the test as at the beginning. As the time for stopping the test draws near, therefore, try to bring the conditions the same as at the start. Do not, however, run the feed pump rapidly in the last few minutes for the test in order to obtain the same water level. If there is a slight difference in level, calculate the weight of water it represents and make the necessary correction to the total weight of water fed. TEMPERATURE OF FEED WATER. Every plant should have a thermometer on the feed line, so as to find the temperature of the feed water. Preferably, this thermom- eter should be of the recording type. If such a form of thermometer is used during the test, it is unnecessary to take the feed temperature at stated intervals, as the record will show the varying temperatures, and so the average feed temperature during the test can easily be found. If there is no thermometer in the feed line, take the feed-water temperature by means of a thermometer hung in barrel 3 (figure 2) by a hook over the edge of the barrel. Head this thermometer every half hour during the test if the feed-water temperature is fairly uni- form; but if it varies considerably, read the thermometer every 15 minutes. The object is to obtain the average feed-water tempera- ture during the test period. Therefore, mark down the tempera- 8 BOILER AND FURNACE TESTING. tures as read at the stated intervals. At the close of the test add the readings and divide their sum by the number of readings and you will have the average temperature of the feed water. STEAM PRESSURE. . Every boiler is fitted with a steam gage by which the pressure is indicated. It is important that the pressure gage be accurate. What is wanted in a test is the average pressure of the steam in the boiler, therefore, observe the pressure at regular intervals, just as with the feed-water temperature, and mark down these gage readings. The sum of the readings divided by the number of readings taken will be the average steam pressure during the test. A recording steam gage is best and makes its own readings. WORKING UP THE TEST. After the boiler test has been made, so as to find the weight of coal burned, weight of feed water used, feed-water temperature and steam pressure, the efficiency, the horsepower, and the economy must be obtained by calculation from the test results. The process of figuring the desired results from the test data is called " working up the test." To illustrate the method used in finding the efficiency, etc., sup- pose that the data obtained from the test are as follows : Length of test hours. . 10 Total weight of coal fired pounds. . 5, 000 Total weight of water evaporated do 35, 000 Average temperature of feed water F . . 180 Average steam pressure, gage pounds per square inch. . 100 The efficiency of any process is always * comparison, or ratio, of the output to the input. In the case of a steam boiler the efficiency is the percentage of the heat supplied in the coal that is usefully employed in making steam. The output of the steam boiler is the heat repre- sented by the quantity of water evaporated by a pound of coal, taking into account the feed temperature and the steam pressure, and input is the amount of heat contained in a pound of the coal used. The efficiency of the boiler is the output divided by the input. The heat contained in a pound of coal is called the "calorific value" or "heating value" of the coal. It can be found by taking a fair average sample of the coal used during the test, as explained in con- nection with weighing the coal, and sending the sample to a chemist, who will make a calorimeter test to determine its heating value. At the end of the test the sample fuel should be spread out on a clean floor and all lumps broken up, so that no pieces are larger than 2 inches maximum diameter. Then the gross sample should be very thoroughly mixed by shoveling, after which it should be spread out in the form of a square of uniform depth and quartered down until BOILER AND FURNACE TESTING. 9 a final average sample is obtained for shipment to a .competent chemist, experienced in fuel analysis. (See Bureau of Mines Tech- nical Paper No. 133.) About 2 quarts of the chemist's sample should be put in air-tight tins or jars for the determination of moisture; the balance of the sample (the total weight of which should be from 10 to 50 pounds, depending on the total weight of coal used in the test) may be packed in a wooden box lined with paper to prevent splinters from mingling with the sample. A duplicate coal sample should be kept at the plant to be used in case of loss of the sample sent to the chemist. The Bureau of Mines has published a bulletin or pamphlet giving the analyses and heating values of the various kinds and grades of coal from all parts of the United States. (Bureau of Mines Bulletin No. 22.) This bulletin can be used to learn the approximate heating value of the coal. Simply find out what district the coal used in the test came from, and its grade, and then refer to the bulletin to obtain the heating value of the coal. If a chemist can be obtained to make a heat test, however, it is better to use the heating value he determines. Suppose that during the test the coal used was run-of-mine bitu- minous having a heating value of 13,500 B. t. u. Every pound of coal fired, then, carried into the furnace 13,500 heat units, and this value therefore is the input to be used in calculating the boiler efficiency. During the test 5,000 pounds of coal was fired and 35,000 pounds of water was fed and evaporated. This means that 35,000 -e- 5,000 = 7 pounds of water was evaporated per pound of coal burned. This is the " actual evaporation," and the heat required to evaporate this 7 pounds of water is the output to be used in calculating the efficiency. Every fireman knows that it takes more coal, and therefore more heat, to make steam with cold feed water than with hot feed water; also, that it is somewhat easier to make steam at a low pressure than at a high pressure. So it is plain that the heat required to evaporate 7 pounds of water into steam depends on two things, namely, (1) the temperature of the feed water and (2) the pressure of the steam in the boiler. From the data of the test, both the aver- age feed-water temperature and the average steam pressure are known, and so it is a simple matter to find out the amount of heat needed to evaporate 7 pounds of water from the average temperature to steam at the average pressure. A pound of water at 212 F. must have 970.4 B. t. u. added to it to become a pound of steam at 212 F., or zero gage pressure. This value, 970.4 B. t. u., is called the latent heat of steam at atmos- pheric pressure, or the heat "from and at 212 F." It is the heat required to change a pound of water/rom 212 F. to steam at 212 F., 75822 18 2 10 BOILER AND FTTBNACE TESTTJTO. and is used by engineers as a standard by which to compare the evaporation of different boilers. In a boiler test the temperature of the feed water is usually some- thing less than 212 F., and the steam pressure is commonly higher than zero, gage. In the test outlined previously, the feed-water tem- perature was ISO F. and the pressure was 100 pounds per square inch, gage. It must be clear, then, that the amount of heat re- quired to change a pound of water at 180 to steam at 100 pounds gage pressure is not the same as to make a pound of steam from and at 212 F. To make allowance for the differences in temperature and pres- sure, the actual evaporation must be multiplied by a number called the " factor of evaporation." The factor of evaporation has -a certain value corresponding to every feed-water temperature and boiler pres- sure, and the values of this factor are given in the accompanying table. Along the top of the table are given the gage pressures of the steam. In the columns at the sides of the table are given the feed-water temperatures. To find the factor of evaporation for a given set of conditions, locate the gage pressure at the top of the table and follow down that -column to the horizontal line on which the feed-water temperature is located. The value in this column and on the horizontal line thus found is the factor of evaporation required. If the feed water has a temperature greater than 212 F., obtain the proper factor of evaporation from the Marks and Davis steam tables. Take the data of the test, for example. The average steam pres- sure is 100 pounds, gage. The average feed-water temperature is 180 F. So, in the table locate the column headed 100 and follow down this column to the line having 180 at the ends, and the value where the column and the line cross is 1.0727, which is the factor of evaporation for a feed-water temperature of 180 F. and a steam pressure of 100 pounds, gage. This factor, 1.0727, indicates that to change a pound of water at 180 F. to steam at 100 pounds requires 1.0727 times as much heat as to change a pound of water at 212 F. to steam at atmospheric pressure. In other words, the heat used in producing an actual evap- oration of 7 pounds under the test conditions would have evaporated 7x1.0727 = 7.5 pounds from and at 212' F. Hence, 7.5 pounds is called the "equivalent evaporation from and at 212' F." per pound of coal used. As already stated, it takes 970.4 B. t. u. to make a pound of steam from and at 212 F. Then to make 7.5 pounds there -would be required 7.5 X 970.4 = 7,278 B. t. u. This is the amount of heat required to change 7.5 pounds of water at 212 F. to steam at zero gage pressure, but it is also the neat required to change 7 pounds BOILEB, AND FURNACE TESTIN-G. 11 of water at 180 F. to steam at 100 pounds gage pressure, because 7.5 pounds from and at 212 F. is equivalent to 7 pounds from 180 F. to steam at 100 pounds. Therefore, the 7,278 B. t. u. is the amount of heat usefully employed m making steam per pound of coal fired, and so it 5s the output. Accordingly, the efficiency of the boiler is Output 7,278 = = =0.54, nearly. In othar words, the efficiency of the boiler is 0.54, or 54 per cent, which means that only a little more than Jhalf of the heat in the coal is usfif ully employed in making steam. The chart shown in figure 3 is given to save the work of figuring the efficiency. If the equivalent evaporation per pound of coal is calculated and the heating value of the coal is known, the boiler efficiency may be found directly from B, 204 106 208 210 212 BOILER AND FURNACE TESTING. Table of factors of evaporation Concluded. Feed temperature, F. Steam pressure in pounds per square inch, gauge. 130 140 150 160 170 180 190 200 32. . 1.2292 1.2261 1.2230 1.2199 1.2168 1.2137 1.2106 1.2075 1.2044 1.2013 1. 1982 1. 1951 1. 1920 1.1889 1.1859 1.1828 1. 1797 1.1766 1.1735 1.1704 1. 1674 1.1643 1. 1612 1. 1581 1.1550 1. 1519 1.1489 1.1458 1.1427 1.1396 1.1365 1.1335 1.1304 1. 1273 1.1242 1. 1211 1.1180 1.1149 1.1119 1.1088 1.1057 1.1026 1.0995 1.0964 1.0933 1.0902 1.0871 1.0850 1.0830 1.0809 1.0789 1.0768 1.0747 1. 0727 1.0706 1.0685 1.0665 1.0644 1.0623 1.0603 1.0582 1.0561 1.0541 1.0520 1.0499 1.0478 1.0458 1.0437 1.2304 1.2273 1.2242 1.2211 1.2180 1.2149 1.2118 1.2087 1.2056 1.2025 1.1994 1.1963 1.1933 1.1902 1.1871 1.1840 1.1809 1. 1778 1.1748 1. 1717 1.1686 1.1655 1.1624 1.1593 1.1563 1.1532 1.1501 1. 1470 1.1439 1.1409 1. 1378 1.1347 1. 1316 1.1285 1.1254 1.1224 1.1193 1. 1162 1. 1131 1.1100 1.1069 1.1038 1.1007 1.0976 1.0945 1.0914 1.0883 1.0863 1.0842 1.0822 1.0801 1.0780 1.0760 1.0739 1.0718 1.0698 1.0677 1.0656 1.0636 1.0615 1.0594 1.0574 1.0553 1.0532 1.0511 1.0491 1.0470 1.0449 1.2315 1.2283 1.2252 1.2221 1.2190 1. 2159 1.2128 1.2097 1.2066 1.2035 1.2005 1. 1974 1.1943 1. 1912 1.1881 1.1850 1.1820 1. 1789 1. 1758 1. 1727 1.1696 1.1665 1.1635 1.1604 1. 1573 1.1542 1. 1511 1. 1481 1.1450 1. 1419 1.1388 1.1357 1. 1326 1.1295 1.1265 1.1234 1.1203 1. 1172 1. 1141 1.1110 1. 1079 1.1048 1.1018 1.0987 1.0956 1.0925 1.0894 1.0873 1.0853 1.0832 1.0811 1.0791 1. 0770 1.0749 1.0729 1.0708 1.0687 1.0667 1.0646 1.0625 1.0605 1.0584 1.0563 1.0542 1.0522 1.0501 1.0480 1.0460 1.2324 1.2293 1.2262 1.2231 1.2200 1.2168 1. 2137 1. 2107 1.2076 1.2045 1.2014 1.1983 1.1952 1.1921 1.1890 1.1860 1.1829 1. 1798 1.1767 1.1736 1.1705 1. 1675 1.1644 1.1613 1.1582 1.1551 1. 1521 1.1490 1. 1459 1. 1428 1. 1397 1.1366 1.1336 1. 1305 1. 1274 1.1243 1. 1212 1.1181 1. 1150 1. 1120 1.1089 1.1058 1. 1027 1.0996 1.0965 1.0934 1.0903 1.0882 1.0862 1.0841 1.0820 1.0800 1.0779 1.0759 1.0738 1.0717 1.0697 1.0676 1.0655 1.0635 1.0614 1.0593 1.0572 1.0552 1.0531 1.0510 1.0490 1.0469 1.2333 1.2302 1.2271 1.2240 1.2209 1.2178 1. 2147 1.2116 1.2085 1.2054 1.2023 1.1992 1.1961 1. 1931 1.1900 1.1869 1.1838 1.1807 1. 1776 1.1746 1. 1715 1.1684 1.1653 1.1622 1. 1592 1.1561 1.1530 1. 1499 1. 1468 1. 1437 1. 1407 1. 1376 1. 1345 1. 1314 1.1283 1. 1252 1. 1221 1.1191 1. 1160 1.1129 1.1098 1.1067 1.1036 1.1005 1.0974 1.0943 1.0912 1. 0892 1. 0871 1.0850 1.0830 1.0809 1.0788 1.0768 1. 0747 1.0727 1.0706 1.0685 1.0664 1.0644 1.0623 1.0602 1.0582 1.0561 1.0540 1.0520 1.0499 1.0478 1.2342 1.2311 1.2280 1.2249 1. 2218 1.2187 1.2156 1.2125 1.2094 1.2063 1.2032 1.2002 1. 1971 1.1940 1.1909 1.1878 1.1847 1.1817 1.1786 1.1755 1.1724 1. 1693 1.1662 1.1632 1.1601 1. 1570 1.1539 1.1508 1.1478 1.1447 1.1416 1.1385 1.1354 1.1323 1.1292 1. 1262 1.1231 1.1200 1. 1169 1.1138 1. 1107 1. 1076 1.1045 1. 1014 1.0984 1.0953 1.0922 1.0901 1.0880 1.0860 1.0839 1.0818 1.0798 1.0777 1.0756 1.0736 1.0715 1.0694 1.0674 1.0653 . 1.0632 1.0612 1.0591 1.0570 1.0550 1.0529 1.0508 1.0487 1.2351 1.2320 1.2288 1.2257 1.2226 1.2195 1.2164 1.2133 1.2102 1.2072 1.2041 1.2010 1. 1979 1.1948 1. 1917 1.1886 1.1856 1.1825 1. 1794 1.1763 1. 1732 1.1701 1. 1671 1.1640 1.1609 1. 1578 1.1547 1. 1515 1.1486 1. 1455 1. 1424 1.1393 1. 1362 1.1332 1.1301 1. 1270 1. 1239 1.1208 1.1177 1.1146 1. 1115 1.1085 1.1054 1.1023 1.0992 1.0961 1.0930 1.0909 1.0889 1.0868 1.0847 1.0827 1.0806 1.0785 1.0765 1.0744 1.0723 1.0703 1.0682 1.0661 1.0641 1.0620 1.0599 1.0579 1.0558 1.0537 1.0516 1.0496 1.2358 1.2327 1.2296 1.2265 1.2234 1.220-2 1.2171 1. 214i 1.211 1.2079 1.2048 1.2017 1.1986 1. 195 5 1.1924 1. 1894 1.1863 1.1832 1.1801 1. 1770 1.1739 1.1709 1.1678 1.1647 1. 1616 1. 1585 1.1555 1. 1524 1.1493 1.1462 1. 1431 1.1400 1.1370 1.1339 1.1308 1. 1277 1.1246 1. 1215 1.1184 1.1154 1.1123 1.1092 1.1061 1.1030 1.0999 1.0968 1.0937 1.0916 1.0896 1.0875 1.1854 1.0834 1. 0813 1.0793 1. 0772 1. 0751 1.0731 1.0710 1.0689 1.0669 1.0648 1.0627 1.0606 1.0588 1.0565 1.0544 1.0524 1.0503 35... 38 41 44 47 50 53 56 59 62 65 68 71 74 77 80 83 86 89 ... 92 95 98 ' 101 104 107 no 113 116 119 122 125 . .. 128 131 134 .. -- 137 140 143 146 149 152 155 158 161 164 167 170 172 174 176 178 180 182 184 186 188 190 192 194 196 198 . -. 200 202 204 '. 206 208 210 212 BOILER AND FURNACE TESTING. 19 PUBLICATIONS ON THK UTILIZATION OF COAL AND LIGNITE. A limited supply of the following publications of the Bureau of Mines has been printed and is available for free distribution until the edition is exhausted. Requests for all publications can not be granted, and to insure equitable distribution applicants are re- quested to limit their selection to publications that may be of especial interest to them. Requests for publications should be addressed to the Director, Bureau of Mines. The Bureau of Mines issues a list showing all its publications available for free distribution, as well as those obtainable only from the Superintendent of Documents, Government Printing Office, on payment of the price of printing. Interested persons should apply to the Director, Bureau of Mines, for a copy of the latest list. PUBLICATIONS AVAILABLE FOB FEB DISTRIBUTION. BULLEMN 58. Fuel briquetting investigations, July, 1904, to July, 1912, by C. A. Wright. 1913. 277 pp., 21 pis., 3 figs. BULLETIN 76. United States coals available for export trade, by Van. H. Man- ning. 1914. 15 pp., 1 pi. BULLETIN 85. Analyses of mine and car samples of coal collected in the fiscal years 1911 to 1913, by A. C. Fieldner, H. I. Smith, A. EL Fay, and Samuel Sandford. 1914. 444pp., 2 figs. BULLETIN 89. Economic methods of utilizing western lignites, by E. J. Bab cock. 1915. 74 pp., 5 pis., 5 figs. BULLETIN 119. Analyses of coals purchased by the Government during the fiscal years 1908-1916, by G. S. Pope. 1916. 118 pp. BULLETIN 135. Combustion of coal and design